title: Roles of cocatalysts in semiconductor-based photocatalytic hydrogen production.
abstract: A photocatalyst is defined as a functional composite material with three components: photo-harvester (e.g. semiconductor), reduction cocatalyst (e.g. for hydrogen evolution) and oxidation cocatalyst (e.g. for oxidation evolution from water). Loading cocatalysts on semiconductors is proved to be an effective approach to promote the charge separation and transfer, suppress the charge recombination and enhance the photocatalytic activity. Furthermore, the photocatalytic performance can be significantly improved by loading dual cocatalysts for reduction and oxidation, which could lower the activation energy barriers, respectively, for the two half reactions. A quantum efficiency (QE) as high as 93 per cent at 420 nm for H₂ production has been achieved for Pt-PdS/CdS, where Pt and PdS, respectively, act as reduction and oxidation cocatalysts and CdS as a photo-harvester. The dual cocatalysts work synergistically and enhance the photocatalytic reaction rate, which is determined by the slower one (either reduction or oxidation). This work demonstrates that the cocatalysts, especially the dual cocatalysts for reduction and oxidation, are crucial and even absolutely necessary for achieving high QEs in photocatalytic hydrogen production, as well as in photocatalytic water splitting.
authors.affiliation: State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, People's Republic of China.
authors.forename: Jinhui
authors.initials: J
authors.lastname: Yang
authors.forename: Hongjian
authors.initials: H
authors.lastname: Yan
authors.forename: Xu
authors.initials: X
authors.lastname: Zong
authors.forename: Fuyu
authors.initials: F
authors.lastname: Wen
authors.forename: Meiying
authors.initials: M
authors.lastname: Liu
authors.forename: Can
authors.initials: C
authors.lastname: Li
keywords: dual cocatalyst; hydrogen production; palladium sulfide; photocatalysis; platinum; water splitting